Embedded Actuators in Composite Airfoils

ABSTRACT

An airfoil having active actuators and at least one morphing area allowing shape change of the airfoil and further allowing for optimization of the airfoil shape at more than one operating condition.

BACKGROUND

Present embodiments relate generally to gas turbine engines. More particularly, but not by way of limitation, present embodiments relate to apparatuses and methods for varying the shape of composite airfoils either actively or both actively and passively.

In turbine engines, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine includes a first stage nozzle and a rotor assembly including a disk and a plurality of turbine blades. The high pressure turbine first receives the hot combustion gases from the combustor and includes a first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles direct the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.

The first and second rotor disks are joined to the compressor by a corresponding rotor shaft for powering the compressor during operation. These are typically referred to as the high pressure turbine. The turbine engine may include a number of stages of static airfoils, commonly referred to as vanes, interspaced in the engine axial direction between rotating airfoils commonly referred to as blades. A multi-stage low pressure turbine follows the two stage high pressure turbine and is typically joined by a second shaft to a fan disposed upstream from the compressor in a typical turbo fan aircraft engine configuration for powering an aircraft in flight.

As the combustion gasses flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The combustion gas is used to power the compressor as well as a turbine output shaft for power and marine use or provide thrust in aviation usage. In this manner, fuel energy is converted to mechanical energy of the rotating shaft to power the compressor and supply compressed air needed to continue the process.

One desirable characteristic for design of gas turbine engines is to always improve efficiency and enhance performance. Due to varying operating condition during operation of the turbine engine, and the fact that changes in turbine blade shape result in different characteristics in performance and efficiency, it would be desirable to design airfoil blades for enhanced operating performance at differing operating instances. For example, one desirable instance to maximize operating efficiency is during takeoff. Another instance to maximize operating efficiency is during cruising condition at flight altitude.

Since known blades are formed of materials which are rigid, design work to maximizing efficiency is typically only available at a single operating instance.

As may be seen by the foregoing, there is a need to optimize performance at multiple operating conditions. Additionally, there is a need to optimize blade designs for multiple operating characteristics which improves performance of the gas turbine engine at various operating conditions.

SUMMARY

Some embodiments of the present disclosure involves an airfoil or blade which is morphable into at least two shapes by way of input from at least an active actuator. Additionally, passive actuation may also be utilized. The airfoil or blade includes a root and an airfoil portion connected to the root. The airfoil has a leading edge, a trailing edge and an outer edge opposite the root. The airfoil is formed of a composite material which is layered and includes at least one morphable area which may change shape through the active actuation.

Some embodiments of the blade include a passive actuation such as, by way of non-limiting example, a shape memory alloy which may be utilized in addition to the active actuation. Other passive actuation may include asymmetric layering of material.

According to certain embodiments of the instant disclosure, the blade may change camber by active actuation, passive actuation or a combination.

All of the above outlined features are to be understood as exemplary only and many more features and objectives of the shape changing airfoil may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the shape changing airfoil will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side section schematic view of an exemplary turbine engine.

FIG. 2 is an isometric view of an exemplary airfoil of a compressor.

FIG. 3 is an isometric view of a first side of an alternative exemplary airfoil.

FIG. 4 is an isometric view of a second side of the exemplary airfoil of FIG. 3.

FIG. 5 is a top isometric view of the airfoil of FIG. 3.

FIG. 6 is an exemplary view of a morphable area of an airfoil.

FIG. 7 is a schematic view of a section of the laminate material.

FIG. 8 is a schematic view of a section of the laminate material.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Present embodiments provide an airfoil which may be formed of various layers of material which has at least one morphable area or portion. For example, one material may be a polymeric matrix composite (PMC). This allows for optimization of the blade shape for more than one operating condition. According to a second embodiment, the material may be a ceramic matrix composite. Other materials may used, such as carbon based materials for example, as well and therefore the description should not be considered limiting. The morphable portion may change shape by way of active actuation, passive actuation or a combination.

The terms fore and aft are used with respect to the engine axis and generally mean toward the front of the turbine engine or the rear of the turbine engine in the direction of the engine axis, respectively.

Referring now to FIGS. 1-8, various embodiments depict apparatuses and methods of changing shape of a composite airfoil utilizing active actuation or a combination of active and passive actuation. The airfoil may be used in a plurality of non-limiting areas of turbine engine including, but not limited to, a turbo fan, a compressor, and turbine. Alternatively, the shape changing airfoil design may include embodiments other than the turbine, such as in a wing, or other airfoil shapes for example.

Referring initially to FIG. 1, a schematic side section view of a gas turbine engine 10 is shown having an engine inlet end 12, a compressor 14, a combustor 16 and a multi-stage high pressure turbine 20. The gas turbine 10 may be used for aviation, power generation, industrial, marine or the like. Depending on the usage, the engine inlet end 12 may alternatively contain multi-stage compressors rather than a fan. The gas turbine 10 is axis-symmetrical about engine axis 26 or shaft 24 so that various engine components rotate thereabout. In operation air enters through the air inlet end 12 of the engine 10 and moves through at least one stage of compression where the air pressure is increased and directed to the combustor 16. The compressed air is mixed with fuel and burned providing the hot combustion gas which exits the combustor 16 toward the high pressure turbine 20. At the high pressure turbine 20, energy is extracted from the hot combustion gas causing rotation of turbine blades which in turn cause rotation of the shaft 24. The shaft 24 passes toward the front of the engine to continue rotation of the one or more compressor stages 14, a turbo fan 18 or inlet fan blades, depending on the turbine design.

The axis-symmetrical shaft 24 extends through the through the turbine engine 10, from the forward end to an aft end. The shaft 24 is supported by bearings along its length. The shaft 24 may be hollow to allow rotation of a low pressure turbine shaft 28 therein. Both shafts 24, 28 may rotate about a centerline 26 of the engine. During operation the shafts 24, 28 rotate along with other structures connected to the shafts such as the rotor assemblies of the turbine 20 and compressor 14 in order to create power or thrust depending on the area of use, for example power, industrial or aviation.

Referring still to FIG. 1, the inlet 12 includes a turbo fan 18 which having a plurality of blades. The turbofan 18 is connected by shaft 28 to the low pressure turbine 19 and creates thrust for the turbine engine 10. Although discussed with respect to the various blades of the turbofan 18, the morphable airfoil shape may be utilized with various airfoils within the turbine engine 10. Additionally, the morphable blade may be utilized with various airfoils associated with structures other than the turbine engine as well.

Referring now to FIG. 2, an isometric view of a compressor blade 30 is depicted. Although a compressor blade is shown and described, other components utilizing an airfoil shape may utilize the described structure. The blade or airfoil 30 includes a root portion 32 which is connected to a, for example, rotor assembly within the compressor 20, the turbofan 18 or the turbine 20 of the turbine engine 10. Extending from the root 32 is an airfoil portion 34 comprising a leading edge 36 and a trailing edge 38. A radially outer end 40 extends between the leading and trailing edges 36, 38. The airfoil 34 includes a suction side 42 and a pressure side 44.

Referring now to FIGS. 3 and 4, an isometric view of an alternative compressor blade is depicted. The blade 30 has the leading edge 36 and the trailing edge 38 which are formed on the airfoil 34 portion of the blade 30. At the bottom of the airfoil 34 is the root 32 which is connected to the rotor assembly. For example, the root 32 may be received in the cavity of a rotor disk or may utilize other mechanical connection with the rotor.

The blade 30 of FIGS. 3 and 4 also comprises a morphable area or portion 50 along a trailing edge 38 which may be changed in profile during operation to change the design shape and improve or optimize efficiency for different portions of flight, such as takeoff and cruise at altitude. Referring briefly to FIG. 5, an upper view of a tip of a fan blade is depicted. The exemplary section depicts the trailing edge 38 which is shown in solid line and in broken line. According to the embodiment of the solid line, the trailing edge 38 has a first or normal position. The broken line depicts the trailing edge 38 moved to a second position by actuation of one of an active actuator, a passive actuator or a combination of both.

Additionally, referring still to FIG. 5, the leading edge 36 may also have a morphing portion 52. Thus, the blade 30 may include a single morphed area or two morphed areas, either of which may be at the leading edge, trailing edge or other portion of the blade 30. These morphing areas 50, 52 and change the camber of the blade 30 during operation. Referring briefly to FIG. 6, a detailed view of the exemplary turbine blade 30 is depicted with the trailing edge 38 shown specifically having morphable area 50 shown in broken line. An angle θ is created between the angle of the trailing edge 38 in its normal position and the morphed position in broken line.

The instant description applies to the exemplary blades as well as other blades which may be within the scope of the present disclosure. Referring again to FIGS. 3-5, the blade 30 including the morphable portion or area 50, located at the trailing edge 38 of the airfoil portion 34,. The morphable area 50 at the trailing edge 38 may alternatively be moved to various positions along the trailing edge 38 between the root 32 and outer edge 58. Similarly, a morphable area 52 along the leading edge 36 may also be located at various positions along the leading edge 36 of the airfoil 34.

The blade 30 is formed of a composite material and may be solid, hollow, partially hollow or may be filled in whole or part with some low density material. The material of the airfoil 34 may be the same or different material from that of the root 32.

Referring to FIG. 7, the blade 30 is formed with multiple layers 70, 72, 74, 76, 78, 80 and 82 of composite material which build upon one another to form the desired shape of at least the airfoil portion 34. Although a number of layers are shown in the depicted embodiment, more layers or fewer layers may be utilized. According to one embodiment, the blade 30 may be formed of a polymeric matrix composite (PMC). According to other embodiments, carbon fibers, glass fibers or some combination thereof may be utilized and may be laid in the chordwise, sparwise, oblique directions or combinations thereof through each or multiple layers. Within the airfoil portion, at a desired morphable location, the airfoil portion 34 may include actuators 60 and 62 which may be active, passive or a combination of both may alternatively be utilized. THe active actuators 62 are embedded in a subsurface manner to cause one or more surface layers to vary in shape when actuated. Additionally, due to the embedded construction of the actuator, the leads 64 may extend from various locations of the blade 30. FIGS. 7 and 8 depict various embodiments in cross section and show the multiple layers defining the morphable areas, for example, morphable area 50. The fibers layers of the morphable portion 50, 52 may be laid in the chordwise, sparwise, oblique directions, or a combination thereof, dependent upon the shape change desired. One or more airfoil regions may be designed to achieve the desired shape change.

The active actuation may occur by way of a piezoelectric actuator which is embedded in the composite laminate material defining the blade 30. The piezoelectric actuator 62 is an active actuator which receives a voltage input and changes shape due to the driving force created by application of voltage to the piezoelectric actuator 62. The actuator 62 is positioned closer to the outer surface of the morphable area to create maximum bending of the airfoil surface. With use of this active actuator 62, more compliant composite materials may be utilized which are more capable of handling strain and require less driving force to deflect. One exemplary material which may be utilized may be S-glass in the morph region 50 and carbon for the remaining region of the airfoil 34. Thus it may be desirable that the morphable portion 50 be formed of at least partially different materials than the remainder of the airfoil portion 34 or the same materials.

Active actuator leads 64 may be embedded in the composite material and terminated outside the structure to provide electrical voltage to the piezoelectric actuator 62, for example. With the actuator 62 embedded the actuator is protected from erosion and other damaging effects which may limit operation of the actuator 62. The leads 64 may exit at any location which does not interfere with performance and which does not damage the lead. Coatings for example may be used to cover the leads and protect such from damage.

Alternate forms of actuation may be utilized. Referring to FIG. 8, additionally, a passive actuator 90 may additionally be utilized in combination with the active actuator 62. Passive actuation may be exemplified by, for example, a shape memory alloy, which passively changes shape due to temperature conditions at specified operating temps, characteristics, or conditions. Thus, during operation, the active actuator 62 may provide all or some driving force to the airfoil 34 causing its change in shape. The passive actuator 90 may additionally cause further morphing of the airfoil 34 at a desired location.

Still a further form of passive actuation may come from asymmetric composite layout where according to such embodiment the asymmetric composite layout may change shape of the airfoil 34 due to for example centrifugal force on the turbine blade 30 during high speed rotation.

Actuation of the active and passive actuator results in a camber change or stagger change of the airfoil 34 through shape change of the morphable portions 50, 52. Camber is generally recognized as the amount of cupping of the blades and stagger is the relative angle of the airfoil to the axial direction of flow. The initial shape of an airfoil 30 prior to changing shape may be optimized such that the bending loads (or moments) are favorable to aid morphing of a fan blade or that the shape at least does not hinder the actuation of the actuator 62. Multi-material systems and varying weight distributions may be optimized such that in-plane load from centrifugal forces due to blade rotation and the induced bending moments aid actuation of the airfoil shape change. In a chordwise cross-section, an initial shape of a blade may be singly curved with a relatively high curvature while the morphed shape is singly curved with a relatively low curvature. Additionally, materials of differing densities or rigidities may be used to aid the morphing of the blade 30.

Laminated structures using composite materials may be used to construct the fan blades 30. These composite materials exhibit various coupling behaviors such as bending and twisting deflections in the direction perpendicular to loading in the presence in plane and bending loads. Such coupling properties of the laminate composite structures may be used to change the airfoil shape of the blade 30. By tailoring the ply or layer layup of the composite material, in both asymmetric and/or multi-material ply orientations, and the region where the ply orientations occur, the airfoil shape can be morphed as a function of rotational speed of fan blade. The airfoil shape for this type of passive actuation may be changed by tailoring the ply or laminate layers in the morphable portion 50 and in one of several manners. First, the layers may be asymmetric through the thickness of the laminated structure. Second, the layup may use two or more distinct materials such as multi-material laminate structure. Third, the weight distribution at various locations of the fan blade may be intentionally changed causing varying force loading due to the centrifugal force during rotation of the turbine blade. Again, this passive actuation may be utilized in addition to the active actuation and may be at one or more various regions of the blade 30 to achieve the airfoil 34 shape change.

While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible.

All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.

It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03. 

What we claim is:
 1. An airfoil, comprising: a root which is connectable to a rotating rotor assembly; an airfoil portion connected to said root, said airfoil having a leading edge, a trailing edge and an outer edge opposite said root; said airfoil portion being formed of composite material and having a morphable area which changes shape by actuation of an active actuator.
 2. The airfoil of claim 1 wherein said active actuator is a piezoelectric actuator.
 3. The airfoil of claim 2 wherein said piezoelectric actuator varies camber by application of voltage.
 4. The airfoil of claim 1 further comprising a passive actuator is a shape memory alloy.
 5. The airfoil of claim 1 wherein said airfoil portion is formed of multiple layers of material.
 6. The airfoil of claim 5 wherein said active actuator is located adjacent an outer layer of said material.
 7. The airfoil of claim 1 wherein said active actuator is located adjacent said trailing edge.
 8. The airfoil of claim 1 wherein said composite material is formed of multiple layers of varying moduli.
 9. The airfoil of claim 1 further comprising first and second actuators.
 10. The airfoil of claim 9 further comprising a shape memory alloy and piezoelectric fiber embedded in said airfoil.
 11. The airfoil of claim 1 wherein said morphable area includes chordwise fibers.
 12. The airfoil of claim 1 wherein said morphable area includes sparwise fibers.
 13. The airfoil of claim 1 wherein said morphable area includes oblique fibers.
 14. The airfoil of claim 1 wherein said airfoil further comprises an asymmetric layering of composite fibers.
 15. An airfoil, comprising: an airfoil portion having a leading edge and a trailing edge; an outer edge spaced from a radially inner portion of said airfoil portion, said outer edge extending between said leading and trailing edge; a morphable portion disposed along said airfoil which is shape changeable; an active actuator disposed within said morphable portion to change the shape of said morphable portion by application of voltage to said active actuator.
 16. The airfoil of claim 15 further comprising a root at said radially inner portion of said airfoil portion.
 17. The airfoil of claim 15, said active actuator changing camber of said airfoil.
 18. The airfoil of claim 17 further comprising a passive actuator.
 19. The airfoil of claim 18 wherein said passive actuator is one of a shape metal alloy or an asymmetric layered material.
 20. An airfoil having a changeable shape, comprising: an airfoil portion having a leading edge and a trailing edge and formed of a plurality of layers of composite material; a morphable portion located between a radially inner end and a radially outer end of said airfoil portion and between said leading edge and said trailing edge; said airfoil portion having an active actuator located within said morphable portion, said active actuator receiving a voltage input to vary a shape to said morphable portion; and, wherein said composite material and material of said morphable portion are at least partially differing materials. 